This invention relates generally to sensors, and more particularly, to methods and systems for calibrating triaxial accelerometers.
Known calibration techniques used in calibrating triaxial accelerometers (triax) generally compensate individual stress sensors for full scale and bias output variations, then mathematically adjust the stress sensor elements so they are oriented orthogonally to each other and are arranged in a Cartesian coordinate system. A rotation transformation then aligns the triax with a known laboratory coordinate system. That is, a triax's coordinate system is rotated to match a laboratory reference frame defined by a calibration fixture. The laboratory reference frame may be associated with the reference frame on a tool face having fiducial marks or common reference surfaces.
Triaxial accelerometer assembly is generally a tedious process. Moreover, because of relatively low sales volume, little investment in automated triaxial assembly processes has been made. Additionally, some components of triaxial accelerometers are durable, such as the frame, but other components, such as the stress sensor elements may be fragile and/or expensive. In addition, coupling one end of a stress sensor element to a triaxial accelerometer chassis and the opposite end of the stress sensor element to a suspended proof mass such that the stress sensor elements are oriented orthogonally to each other may be difficult. Moreover, the process of orthogonally orienting the stress sensor elements with respect to each other is generally subjective and as a result, small misalignments may be created between stress sensor elements. Such misalignments may adversely affect the triaxial accelerometer's calibration which decreases its measurement accuracy.